42 ON DORSO-LUMBAR SPRAIN IN THE HORSE. 
sprain of the reins. In his post-mortem examination, I dis¬ 
covered that the great psoas muscle on the left side had become 
considerably augmented in volume, that its tissue possessed less 
firmness, and that its cellular sheath was reddened and infil¬ 
trated. In its interior I found several clots of black blood, 
floating in a cavity whose parietes were thin, to which they 
were adherent by red filaments, which proved to be the extremi¬ 
ties of lacerated muscular fibres. 
This case, in my opinion, is not one to our point. I do not 
think that the reported alteration in the psoas muscle had any 
thing to do with the sprained loins. I have seen such changes 
present on several occasions without any such affection. 
Case II. is one wherein there was present spontaneous and 
recent rupture of the internal ligaments of the hip-joint. The 
symptoms observed, on account of the wry action of the hind 
quarters, gave rise to the belief that there was sprain of the 
reins or engorgement of the spermatic cords. ' 
In concluding this enumeration of the lesions which have 
been adduced as explanatory of broken back, I may mention 
that I have observed this symptom present in a horse who had 
an obliteration of the posterior aorta at the place of its bifur¬ 
cation. 
Properly speaking, broken back is so remarkable and charac¬ 
teristic, that it is symptomatic of lesions of the spinal chain 
in general. I shall, however, here exclude—1st, what are 
called luxations, for reasons I have already given; and, 2dly, 
fractures, the symptoms of which are such as either to para¬ 
lyse the animal or deprive it of all power of standing. So 
that there remains but strains, or rupture of the intervertebral 
discs; accidents which alone, in my opinion, have a right to be 
called strains of the reins, or clorso-lumbar sprains. In fact, 
this proves to be the seat of lesion in the great majority of 
horses exhibiting sprained back when they come to be de¬ 
stroyed; and if I do not say, in every case, it is because Gar- 
sault’s imperfect observations on the spinal muscles leaves one 
in doubt but that they may be implicated, though I do not 
regard that as the principal or essential lesion. But now let us 
inquire into the seat of the lesion. 
The Lesions are situated sometimes in the lumbar region, 
sometimes in the dorsal, sometimes in both regions together. 
The extent of the lesion depends, without doubt, upon the 
modus operandi of the cause. The lesion is frequently found 
opposite to the articulation of the twelfth with the thirteenth 
dorsal vertebra; an observation which confirms what I have 
asserted takes place in the spinal chain under the influence of 
pression acting vertically, from above downward, upon it; it is 
likewise in this same part that fractures happen through the 
violence of muscular effort. In fact, this is the articulation 
